Reconstruction of individual cumulative radon exposures by low-level in vivo measurements and biokinetic modeling

In vivo skull measurements of ²¹⁰Pb have been performed to assess the individual, chronic exposures of two persons living for 28 years in a house with a distinctly enhanced radon concentration of more than 10,000 Bq/m³. A partial body counter consisting of 4 HPGe detectors, which were placed close to parietal positions of the head, was used in the study. The lower limit of detection of ²¹⁰Pb activity in the skeleton was found to be 40 Bq. Lead-210 activities of up to 152 Bq were found in the test persons, whereas no activity could be measured in an unexposed control person. The cumulative uptake of ²¹⁰Pb into the body was assessed for each single test person by using the ICRP respiratory tract and the biokinetic models. A fairly good agreement (within a factor of 2) between in vivo measurements and model was achieved for these two test persons. The technique used in the study may be a useful tool to evaluate assumptions, which have to be made for the reconstruction of individual, cumulative exposures to high radon concentrations.